chore(deps-dev): bump postcss from 8.4.21 to 8.4.31 in /web (#436)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.21 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.4.21...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:development
...

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web/package.json

@@ -41,7 +41,7 @@
     "autoprefixer": "^10.0.2",
     "cross-env": "^7.0.3",
     "csstype": "^3.0.10",
-    "postcss": "^8.1.0",
+    "postcss": "^8.4.31",
     "prop-types": "^15.8.1",
     "rimraf": "^3.0.2",
     "@types/node": "^16.11.26",